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Who Are We?

With over 37 years of experience and more than 225 fulltime employees across its six locations in South Western Ontario, Great Northern Insulation (GNI) services homeowners and industry professionals in the residential, commercial, industrial and agricultural sectors. GNI offers a complete list of building envelope products and services for new and retrofit projects to increase energy efficiency, comfort, and structural durability. These solutions include insulation, air sealing, fireproofing, panel and cladding, building diagnostics, thermography, and more.

As a member of the Mill Street and Co. group of Companies, it is our collective vision to be the number one Construction & Building Services Provider in Canada. Here is a list of our related companies intent on fulfilling that vision:



Proudly Serving all of Southern Ontario

GTA; South Central Ontario

450 Industrial Dr.

Milton, Ontario

Canada L9T 5A6

TOLL FREE: 1-800-265-1914